Utility knife blade

ABSTRACT

A utility knife blade includes a portion made of a first material; and an elongated portion made of a second material, the second material being harder than the first material and coated on the first material by melting a powder of the second material on the first material, the elongated portion forming the tip of the blade, wherein the second material includes tungsten carbide particles embedded in a soft binder, and wherein the size of at least 90% of the tungsten carbide particles is lower than about 5 micrometers.

FIELD

The invention relates to a utility knife blade and a method ofmanufacturing the same.

BACKGROUND

Cutting devices, such as utility knives, have been developed for use invarious applications, such as, for example, construction, packaging andshipping, carpet installation, as well as other purposes.

The use of tungsten carbide as cutting material in cutting devices iswell known in the art. Tungsten carbide is used extensively in variouscutting, drilling, milling and other abrasive operations due to its highabrasion resistant properties. Conventional cutting tools like power sawblades have tungsten carbide inserts brazed onto the blade teeth. Thismakes the actual cutting surface extremely hard and durable. However,brazing is not a suitable process for mounting tungsten carbide insertson many cutting tools, such as utility blades.

SUMMARY

One aspect of the invention involves a utility knife blade including acoating of tungsten carbide. Another aspect of the invention involves amethod of manufacturing a blade having a hard coating deposited on itsedge. The method includes depositing a hard material, e.g. tungstencarbide, onto the edge of a cutting tool and then sharpening the edgesuch that the surface is entirely made of the hard material, e.g.tungsten carbide, after sharpening.

In an aspect of the invention, there is provided a utility knife bladeincluding a portion made of a first material; and an elongated portionmade of a second material, the second material being harder than thefirst material and coated on the first material by melting a powder ofthe second material on the first material, the elongated portion formingthe tip of the blade, wherein the second material includes tungstencarbide particles embedded in a soft binder, and wherein the size of atleast 90% of the tungsten carbide particles is lower than about 5micrometers.

In an aspect of the invention, there is provided a manufactured bladefor a cutting tool comprising: a first elongated portion made of a firstmaterial; and a second elongated portion made of the first material anda second material, the second material being harder than the firstmaterial and deposited on the first material, the second elongatedportion forming the tip of the blade, wherein the first elongatedportion defines a first cutting edge having a first angle and the secondelongated portion defines a second cutting edge having a second angle,the first angle being smaller than the second angle, and wherein atransition from the first angle to the second angle occurs in a regionof the blade made of the first material that has been re-hardened duringdeposition of the second material on the first material.

In another aspect of the invention, there is provided a manufacturedblade for a cutting tool comprising: a portion made of a first material;and an elongated portion made of the first material and a secondmaterial, the second material being harder than the first material anddeposited on the first material, the elongated portion forming the tipof the blade, wherein the elongated portion forms a facet of the bladethat is oriented at a non-zero angle relative to a surface of theportion of the blade, and wherein a transition from the surface of theportion to the facet of the elongated portion occurs in a region of theblade made of the first material that has been re-hardened duringdeposition of the second material on the first material.

In yet another aspect of the invention, there is provided a manufacturedblade for a cutting tool comprising: a portion made of a first materialand having a hardness in a range from about 500 Hv to about 700 Hv; andan elongated portion made of the first material and a second material,the second material being harder than the first material and depositedon the first material and having a hardness greater than about 1,100 Hv,the elongated portion forming the tip of the blade, wherein theelongated portion forms a facet of the blade that is oriented at anon-zero angle relative to a surface of the portion of the blade, andwherein the second material includes tungsten carbide particles thathave a size less than about 5 micrometers.

These and other aspects, features, and characteristics of the presentinvention, as well as the methods of operation and functions of therelated elements of structure and the combination of parts and economiesof manufacture, will become more apparent upon consideration of thefollowing description and the appended claims with reference to theaccompanying drawings, all of which form a part of this specification,wherein like reference numerals designate corresponding parts in thevarious figures. It should be appreciated that the microphotographsherein are to scale (relative proportions are depicted). It is to beexpressly understood, however, that the drawings and microphotographsare for the purpose of illustration and description only and are notintended as a definition of the limits of the invention. As used in thespecification and in the claims, the singular form of “a”, “an”, and“the” include plural referents unless the context clearly dictatesotherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 shows a utility blade in accordance with an embodiment of theinvention;

FIG. 2 a shows a cross section of a utility blade in accordance with anembodiment of the invention;

FIG. 2 b shows a hardness profile of the utility blade and amicrophotograph image of the blade in accordance with an embodiment ofthe invention;

FIG. 3 shows a flowchart for manufacturing a blade of a cutting tool inaccordance with an embodiment of the invention;

FIG. 4 shows a steel strip in accordance with an embodiment of theinvention;

FIG. 5 shows a deposition station configured to deposit a hard metal(e.g. tungsten carbide) on an edge of a steel strip in accordance withan embodiment of the invention;

FIG. 6 a shows a cross section microphotograph image of the blade afterdeposition of hard material and before grinding in accordance with anembodiment of the invention;

FIG. 6 b shows a cross section microphotograph image of the blade afterdeposition of hard material and before grinding;

FIG. 6 c shows a cross section microphotograph image of the blade aftergrinding the blade of FIG. 6 a in accordance with an embodiment of theinvention;

FIG. 6 d shows a cross section microphotograph image of the blade aftergrinding the blade of FIG. 6 b;

FIG. 7 shows a dispenser for use in the apparatus of FIG. 5 inaccordance with an embodiment of the invention;

FIG. 8 a shows a cross section microphotograph of the blade obtained fora 250 mm/minute deposit of second material in accordance with anembodiment of the invention;

FIG. 8 b shows a cross section microphotograph of the blade obtained fora deposit of second material at a speed greater than 250 mm/minute;

FIG. 8 c shows a cross section microphotograph of the blade of FIG. 8 b.

FIG. 9 a is a perspective microphotograph of an individual powderparticle before deposition having a nominal size of about 30micrometers;

FIG. 9 b is a perspective microphotograph of a plurality of powderparticles;

FIG. 9 c shows a cross section microphotograph of a powder particlehaving a nominal size of about 30 micrometers;

FIG. 9 d is a microphotograph illustrating tungsten carbide particlesembedded in the cobalt carrier and having a size less than about 1micrometer; and

FIG. 9 e shows laser size diffraction data for two types of powder(powder a and powder b) having the same chemical composition.

DETAILED DESCRIPTION

FIG. 1 shows a utility knife blade 100 in accordance with an embodimentof the invention. Utility knife blade 100 defines a back edge 5, acutting edge 10 and two side edges 15 and 20 located on opposite sidesof the blade relative to each other. As shown in FIG. 1, the back edge5, the cutting edge 10 and the two side edges 15 and 20 define anapproximately trapezoidal configuration, although this invention is notlimited to blades on any particular shape. For example, other shapes(e.g. rectangular) are contemplated. The utility knife blade 100 alsogenerally has a main portion 7 and cutting edge portion 17. As will bedescribed in more detail hereinafter, the cutting edge portion 17 isformed by two elongated portions that are oriented at different anglesrelative to the main portion 7 and that extend lengthwise, generallyparallel to the tip 18. Specifically, the cutting edge portion 17includes a first elongated portion 25 and a second elongated portion 30formed at the tip 18 of the blade 100. It will be appreciated thatembodiments of the invention are not limited to the configuration ofFIG. 1. Just for example, it is envisioned that in another embodiment,the cutting edge portion 17 includes a single elongated portion, whichcorresponds to the second elongated portion 30. In yet anotherembodiment, the cutting edge portion 17 includes more than two elongatedportions.

Referring now to FIG. 2 a, this figure shows a cross section of theblade 100 taken along the line AA′ of FIG. 1. As shown in FIG. 2 a, theblade 100 further defines substantially planar top and bottom portions35 and 40 that are located on opposite sides of the blade 100 relativeto each other. The first elongated portion 25 includes first facets 45 aand 45 b that are contiguous with, respectively, planar top and bottomportions 35 and 40. Facet 45 a lies between first exterior point 27 aand second exterior point 26 a. Similarly, facet 45 b lies between firstexterior point 27 b and 26 b. The second elongated portion 30 includessecond facets 50 a,b that are contiguous with, respectively, firstfacets 45 a,b. The first facets 45 a,b define a first angle α in themanner illustrated (where line 29 a is parallel to the central axis X)and the second facets 50 a,b define a second angle α′ in the mannerillustrated (angle between facet 50 a and central axis X). The firstangle α is smaller than the second angle α′. In an embodiment of theinvention, the first angle α is between 6° and 10° (such as about 8°)and the second angle α′ is between 12° and 16° (such as about) 14°.

In an embodiment of the invention, the first elongated portion 25 (whichmay be considered to generally reside in the region defined by bluntpoints 26 a, 26 b, 27 a, 27 b) and the main portion 7 of the blade 100are made of a same first material 55, while the second elongated portion30 (which may be considered to reside in the regions defined by points26 a, 26 b and tip 18) is made of the first material 55 and of a secondmaterial 60 that has a hardness greater than the first material 55. Inan embodiment, the first material 55 is steel and the second material 60is tungsten carbide. In addition, the blade 100 defines an intermediateor overlapping portion 65 arranged across the junction between the firstelongated portion 25 and the second elongated portion 30. In oneembodiment, the intermediate portion 65 may be formed of the firstmaterial 55. The first material 55 in the intermediate portion 65 has ahardness greater than the hardness of the first material 55 outside theintermediate portion 65 but lower than the hardness of the secondmaterial 60. In an embodiment of the invention, the intermediate portion65 corresponds to a region of the first material 55 that has beenre-hardened during formation of the second material 60. It should beappreciated that while the figures illustrate the boundaries betweenregions and/or materials as distinct lines, in actual practice suchboundaries may be irregular and may also be broader transitional regionsas will be appreciated by those skilled in the art.

In FIG. 2 a, the deposition of the second material 60 (e.g. tungstencarbide) in accordance with an embodiment of the invention provides ablade 100 that has a surface of second material 60 (e.g. tungstencarbide) that is flush with the remaining surface of the blade. Thesecond material 60 (e.g. tungsten carbide) may be welded to the firstmaterial 55 so as to form a seamless transition between the secondmaterial 60 (e.g. tungsten carbide) and the core first material 55 ofthe blade 100.

In FIGS. 1 and 2 a, the transition (e.g., at points 26 a and/or 26 b)from the first angle α to the second angle α′ or from the first facets45 a,b to the second facets 50 a,b occurs in the intermediate region 65of the blade 100 made of the first material 55 that has been re-hardenedduring deposition of the second material 60 on the first material 55.Changing the cutting edge angle in the re-hardened area of the firstmaterial 55 rather than in the second material 60 facilitates thegrinding operations and limits the amount of the second material 60 inthe second elongated portion 30. In an embodiment, the second material60 occupies a volume greater than 50% of a total volume of the secondelongated portion 30. In another embodiment of the invention, the secondmaterial 60 occupies a volume greater than 70% of a total volume of thesecond elongated portion 30.

In one embodiment of the invention, the thickness of the second material60 in the second elongated portion 30 as defined by the distance dbetween the tip 18 of the blade 100 and the intermediate portion 65after grinding is in a range of from about 0.1 to 0.3 mm. In anembodiment, it will be appreciated that the distance d can extend to theblunt points 26 a, 26 b (as seen along the central axis X) so that theentire second elongated portion 30 is made of the second material 60.The thickness of the intermediate portion 65, which corresponds to there-hardened portion of the first material 55, is in a range of fromabout 0.3 and 0.4 mm. Further, the thickness of the main portion 7 ofthe blade 100 is between 0.4 mm and 0.8 mm (such as about 0.6 mm). Itwill be appreciated that these thicknesses may vary in other embodimentsof the invention depending on the type of materials used to manufacturethe blade and the geometry of the blades.

In an embodiment of the invention, the hardness of the second material60 is greater than 1,100 Hv and the hardness of the first material 55 isin a range of from about 500 Hv to about 700 Hv. In another embodiment,the hardness of the first material is in a range of from about 630 Hv toabout 650 Hv. For example, referring to FIG. 2 b, this figure shows ahardness profile of the blade 100 in accordance with an exampleembodiment. The profile was determined for a blade including tungstencarbide as second material 60. The hardness profile comprises 4 hardnessregions. The first hardness region A is defined by the second material60 and extends, in this embodiment, axially (e.g., along axis X in FIG.2 a) to a depth at which the blunt points 26 a, 26 b so that the entiresecond elongated portion 30 is made of the second material 60. Thisembodiment is different from that in FIG. 2 a, wherein the firsthardness region (defined by the second material 60) does not extend allthe way to the blunt portions 26 a, 26 b. The second and third hardnessregions B and (C1 and C2) are the heat affected zones from the weldingoperation. The hardness profile in these regions is determined by thegradient of temperatures that is generated by the welding operation. Thesecond hardness region B corresponds to an untempered martensite regionin which the first base material 55 has been fully rehardened. As aresult, the first material has become austenitic during the weldingprocess and has a hardness that is greater than the first material 55 inregion C1. Immediately below region B lies regions C1 and C2. Regions C1and C2 have not attained a sufficiently high temperature to becomeaustenitic during the welding process, but have reached a temperaturehigher than the tempering temperature used in the original strip heattreatment process. As a result, regions C1 and C2 have been overtemperedcompared with the non heat affected region of the base material 55. Thisproduces a lower hardness zone compared with the regions B and the nonheat affected region of the base material 55. It is noted that theovertempering is greater in the region C1 than in the region C2 as aresult of a gradient of temperatures affecting the blade. In FIG. 2 b,the area of retempering exists within the first facet 45 a and 45 b(area C1) and beyond into the body of the blade 55 (area C2).

The laser deposition welding process in one embodiment provides ashallow level of heat penetration to reduce or eliminate distortion ofthe substrate. With the laser welding process, the heat produced at thesurface of the strip is sufficient to melt both the powder binder andthe strip surface. The region immediately behind the weld pool attains atemperature sufficiently high to transform to austenite while in thearea of influence of the laser. But the body strip below the surfaceremains relatively cool, so that when the strip exits the influence ofthe laser beam, heat is drawn back into the cold strip at a rate whichexceeds the critical cooling rate for hardening. This results in an areaof untempered martensite (area B), with a typical hardness in the rangeof HV 750−900.

In one embodiment, only one side of the blade may be ground. Inaddition, for example, only point 26 a may be formed, while point 26 amay be omitted (e.g. a straight line formed on the opposite side of theblade between tip 18 and point 45 b).

Referring now to FIG. 3, this figure shows a flow chart of a process 300of manufacturing the blade 100 according to an embodiment of the presentinvention. In the process 300 of manufacturing a blade, a strip of steelblade stock material (i.e. the first material 55), from which aplurality of blades are produced, is provided at step 320. In oneembodiment, the steel is provided in a coil form, for example, to renderthe strip more compact to facilitate handling. In an embodiment of theinvention, the first material is made of steel and may include a highcarbon steel such as, for example, steel grade ANSI 1095 or a low alloysteel (e.g. AISI 4147), although it is contemplated that other types ofmaterials could be used in other embodiments of the invention. Thelength of the strip in the coil can be as long as 1 km or more. Thestrip may also be provided in a multiple coils configuration, themultiple coils being welded end to end. The dimension of the strip canbe selected according to desired dimensions of the blade 100. Forexample, the strip can have a width of 19 mm and a thickness of 0.6 mm.However, the strip can have other dimensions depending on the intendeduse of the blade that would be formed from the steel strip. In anembodiment of the invention, the steel strip is provided with a maximumhardness of about 300 Hv.

At step 330, the steel strip material is delivered to a punch presswhere a plurality of openings are stamped into the strip to defineattachment points employed to retain the blade in a cartridge or onto ablade carrier for utility knife. In addition, a brand name, logo orother indicia may also be stamped thereon. The steel strip is thenscored at step 340 to form a plurality of axially spaced score lines,wherein each score line corresponds to a side edge of a respective bladeand defines a breaking line for later snapping or cutting the scoredstrip into a plurality of blades. FIG. 4 is a schematic representationof a portion of the strip made of the first material (or steel strip)400 that shows the score lines 410. The score lines define individualblades 100 that have a trapezoid shape. Other forms and shapes such asparallelogram blades, hook blades, etc. may also be obtained with aselection of an appropriate scoring configuration.

In one embodiment, the scoring and piercing procedures of steps 330 and340 can be combined into a single stamping operation.

After scoring and piercing the steel strip, the process proceeds to step350, where the steel strip 400 is hardened prior to depositing thesecond material. The heat treatment prior to deposition of the secondmaterial 60 is represented by steps 350-390 in FIG. 3 and is designed sothat the blade 100 can absorb the stress experienced by the blade duringdeposition of the second material 60.

As shown in FIG. 3, the coil of pressed steel strip of blade stock isthen fed at step 350 through a heat treatment line to harden the steelstrip material. In this process, the steel is run off of the coil andpassed through a hardening furnace which heats the steel to atemperature above a transition temperature. The transition temperatureis the temperature at which the structure of the steel changes from abody centered cubic structure, which is stable at room temperature, to aface centered cubic structure known as austenite (austenitic structure),which is stable at elevated temperatures, i.e. above the transitiontemperature. The transition temperature varies depending on the steelmaterial used. In an embodiment of the invention, the heating to hardenthe steel strip is performed at a temperature between about 800° C. and900° C. For example, for a grade 1095 steel, the transition temperatureis approximately 890° C.

In an embodiment of the invention, the length of the hardening/heatingfurnace is approximately 26 feet (approximately 8 meters). The steelstrip travels at a speed approximately between 16 and 22 feet per minute(approximately between 5 and 7 meters per minute). A controlledatmosphere of, for example, “cracked ammonia,” which containsessentially nitrogen and hydrogen, is provided in the furnace to preventoxidation and discoloration of the steel strip. Although cracked ammoniamay be used to prevent oxidation and discoloration other gases may beused, such as but not limited to, “a scrubbed endothermic gas” or“molecular sieved exothermic gas.”

In an embodiment of the invention, the heating of the steel strip toharden the steel strip is performed for a time period between about 75and 105 seconds.

After exiting the heating (hardening) furnace, at step 360, the heathardened steel strip is quenched. In an embodiment of the invention, thehardened steel strip is passed between liquid cooled conductive blocksdisposed above and below the steel strip to quench the steel strip. Inan embodiment of the invention, the heat hardened steel strip is passedthrough water-cooled brass blocks with carbide wear strips in contactwith the steel strip to quench the steel. The brass blocks cool thesteel strip from the hardening temperature, for example (approximately890° C.), to ambient temperature (approximately 25° C.) at a speed abovea critical rate of cooling. The critical rate of cooling is a rate atwhich the steel is cooled in order to ensure that the austeniticstructure is transformed to martensitic structure. A martensiticstructure is a body centered tetragonal structure. In the martensiticstructure, the steel is highly stressed internally. This internal stressis responsible for the phenomenon known as hardening of the steel. Afterhardening, the hardness of the steel which was originally less thanapproximately 300 Hv (before heat treatment) becomes approximately 850Hv (approximately 63 HRC). In an embodiment of the invention, thequenching of the steel strip is performed for about 2 to 4 seconds. Inanother embodiment of the invention, a gas or a liquid is used to quenchthe steel strip.

At step 370, the hardened steel strip then passes through a temperingfurnace which heats the steel to a temperature between 150° C. and 400°C., for example about 350° C. This process improves the toughness of theblade and reduces the blade hardness, depending on the temperingtemperature selected.

In an embodiment of the invention, the length of the tempering furnaceis approximately 26 feet (approximately 8 meters). The steel striptravels at a speed approximately between 16 and 22 feet per minute(approximately between 5 and 7 meters per minute). A controlledatmosphere of, for example, “cracked ammonia,” which containsessentially nitrogen and hydrogen, is provided in the furnace to preventoxidation and discoloration of the strip. Although cracked ammonia maybe used to prevent oxidation and discoloration other gases may be used,such as but not limited to a “scrubbed endothermic gas” or “molecularsieved exothermic gas”. In the embodiment of the invention, the heatingof the strip to temper the strip is performed for a time period betweenabout 75 and 105 seconds.

After exiting the heating (tempering) furnace, at step 380, the hardenedand tempered steel strip is quenched. In an embodiment of the invention,the hardened and tempered steel strip is passed between liquid cooledconductive quench blocks disposed above and below the steel strip toquench the steel strip. In an embodiment of the invention, the heathardened and tempered steel strip is passed through water-cooled brassblocks with carbide wear strips in contact with the steel strip toquench the steel. The brass blocks cool the steel strip from thetempering temperature, for example (approximately 150° C. to 400° C.,for example 350° C.), to ambient temperature (approximately 25° C.) at aspeed above a critical rate of cooling to prevent oxidation of the steelsurface.

It will be appreciated that the temperature ranges of the hardening andtempering operations at steps 350 and 380 can be controlled to obtainthe desired blade hardness for the main portion 17 of the blade 100 andto reduce or prevent blade distortion during deposition of the secondmaterial 60. For example, if the hardness of the blade 100 is too low,the blade may bend and it may be difficult to snap off the individualblades 100 from the steel strip. Conversely, if the hardness of theblade 100 is too high, blade distortion may occur during deposition ofthe second material 60 on the first material 55. In one embodiment ofthe invention, the temperature of the hardening and tempering operationsat steps 350 and 380 are controlled such that the resulting strip offirst material 55 has a hardness, before deposition of the secondmaterial 60, in a range of from about 500 to 700 Hv. In a furtherembodiment, the hardness of the resulting strip of first material 55 isin a range of from about 630 to 650 Hv.

The coil of quenched steel strip is then continuously fed at step 390 toa second material 60 deposition station that is configured to apply acoating of the second material 60 to an edge of the steel strip. Thehard material 60 has a hardness that is significantly greater than thesteel strip. In one embodiment of the invention, the hardness of thehard material is at least 1100 Hv.

In one embodiment, the strip of the first material 55 is heat treatedprior to deposition to reduce the likelihood that heat treating a softcoated strip with a second material would introduce cracks in the blade100 or cause the coating of second material 60 to possibly disintegrate.

Referring now more particularly to FIG. 5, this figure is a schematicrepresentation of a deposition station, generally indicated at 500, fordepositing a coating of hard material, e.g. tungsten carbide, onto theedge portion 17 of the moving strip 400 made of the first material 55,in accordance with an embodiment of the invention. The depositionstation 500 includes a radiation source 505 configured to provide a beamof radiation 555 onto the strip 400. The deposition station 500 furtherincludes a projection system 525 configured to project and focus thebeam of radiation 555 onto a target portion of the steel strip 400.

Referring back to FIG. 5, the radiation source 505 is configured tooutput a radiation beam with sufficient power and energy to melt thestrip 400. In one embodiment, the radiation source is a solid state disklaser that outputs a beam of radiation in the infra-red (IR) range, witha wavelength of 1.03 micrometer. The laser is high pulse rate laser thatoutputs the beam continuously. In another embodiment of the invention, afiber laser with a wavelength of 1.06 micrometer may be used. In yetanother embodiment of the invention, a CO₂ laser with the principalwavelength bands centering around 9.4 and 10.6 micrometers may be used.The power of the CO₂ laser may be in the range of about a few kWatts,for example between 1 and 8 kWatts. In one embodiment, the power of theCO₂ laser is about 6 kWatts. Alternatively, a laser operating in theultra-violet (UV) range could also be used in another embodiment of theinvention such as, for example, a UV laser with a wavelength lower than400 nm. Examples of UV lasers include excimer lasers.

It will be appreciated that the source of radiation 505 is not limitedto a light source. For example, in an embodiment of the invention, anelectron beam source or a plasma source may also be used in thedeposition station 500. In this implementation, the electron beam sourceis configured to provide a beam of electrons with sufficient energy andpower to melt the strip 400.

The beam of radiation 555 outputted by the radiation source 505 isdirected to a projection system 525 that is configured to focus the beamonto the edge of the moving strip 400. The energy of the projected beam555 that is concentrated on the edge 17 of the strip 400 is used to meltthe target portion of the strip, and when used, the binder within thefeed powder 542. In one embodiment of the invention, the spot of theradiation beam focused on the strip 400 has substantially the samethickness as the strip. For example, in one embodiment, the spot size isabout 0.6 millimeter.

The projection system 525 may include various types of opticalcomponents, such as refractive, reflective, magnetic, electromagnetic,electrostatic or other types of optical components, or any combinationthereof, to direct, shape, or control the radiation. In the event theradiation source is an electron beam source, electromagnetic lenses maybe used to control and focus the beam 555.

It will be appreciated that the projection system 525 may be integralwith the radiation source 505. The projection system 525 is preferablymounted to a frame that is stationary, although it is contemplated thatone or more optical elements of the projection system 525 may be movableto control the shape of the projected radiation beam 555.

A dispenser or deposition head 520, arranged between the radiationsource 505 and the strip 400, is configured to supply a mixture 542 ofhard material and a binder element, collectively referred to as thesecond material 60, to the thin edge 17 of the strip 400. The dispenser520 has a generally hollow shape to allow the beam of radiation 555 topass therethrough.

In an embodiment of the invention, the powder including the secondmaterial is a pre-blended mixture of the cobalt binder, chromium and thetungsten carbide. The source powder particle size should be high enoughto reduce the likelihood of nozzle blockage. In an embodiment, thepowder particle size (e.g. the diameter, equivalent diameter or largestdistance between two extremities of a particle) is in a range betweenabout 15 and 45 micrometers, for example nominally about 30 micrometers.FIG. 9 a shows an individual powder particle before deposition having anominal size of about 30 micrometers. The tungsten carbide particles,after deposition, remain largely unchanged. Only the binder is melted toproduce the solid welded deposit. In an embodiment, the second material60 has the following composition: cobalt in a range from about 8 and12%, such as 9.5 to 10.5%, chromium in a range from about 2 to 5%, suchas 3.5 to 4.5%, carbon in a range of from about 3 to 7%, such as 5 to5.5% and tungsten (in an amount corresponding to the remaining balance).Other embodiments of the invention may use other percentage of tungstencarbide powder, or different materials.

In one embodiment, the powder particles have substantially the samemorphology in terms of size (e.g. the diameter, equivalent diameter orlargest distance between two extremities of a particle), shape andchemical composition to facilitate a uniform deposit of tungsten carbideon the blade. Referring to FIG. 9 b, this figure shows powder particleshaving substantially the same morphology. In an embodiment, the powderparticles are substantially spherical and have a density sufficientlylow so that the powder is able to rapidly melt under the action of thelaser beam. This favors the rapid formation of a uniform deposit oftungsten carbide on the blade. However, the powder density should alsobe high enough to facilitate the particles falling under the action ofgravity and reach favorable flow rates. For example, in an embodiment,the powder density is high enough to obtain flow rates of powderparticles on the blade greater than about 3 grams/second, in anotherembodiment greater than about 4 grams/second and in another embodimentgreater than about 5 grams/second. In an embodiment, the powder has adensity between about 2 and 6 grams per cubic centimeter. For example,in an embodiment, the powder density is between about 3 and 5 grams percubic centimeter, for example, about 4 grams per cubic centimeter. In anembodiment, the substantially low density is obtained by usingsubstantially porous powder particles. FIG. 9 c shows a cross section ofa powder particle according to an embodiment of the invention. As shownin FIG. 9 c, the particle powder, which has a spherical shape, issubstantially hollow.

In one embodiment it may be desirable that the particle size (e.g. thediameter, equivalent diameter or largest distance between twoextremities of a particle) of the tungsten carbide particle or at least90% of the tungsten carbide particles (and in another embodiment atleast 99%) within the powder can be less than about 5 micrometers, andin another embodiment at least 90% (and in another embodiment at least99%) equal to or less than about 2 micrometers to facilitate grinding toa sharp edge. In an embodiment, the powder is manufactured asagglomerated—sintered to form a powder that has individual tungstencarbide particles within a metal matrix or binder. In an embodiment, thesize of these tungsten carbide is 95%, and in another embodiment 99%less than 2 micrometers, as measured by laser size diffraction. Inparticular, the size and distribution of the tungsten carbide particleswithin each powder particle can, in one embodiment, be substantiallyuniform in order to favor the formation of a uniform deposit of tungstencarbide on the blade. FIG. 9 d shows tungsten carbide particles embeddedin the cobalt binder and having a size less than about 1 micrometer. Theperformance of the cutting edge of the blade 100 is at least partiallydependent on the size of the particles of the second material (e.g.tungsten carbide) embedded in the matrix of softer binder (e.g. cobalt,nickel, iron, . . . ). Powders containing large particles are generallyless suitable because the carbide particles themselves may not be ableto be ground to a sharp edge and the bonding matrix, being soft, may notbe able to withstand the grinding forces.

Referring to FIG. 9 e, this figure shows laser size diffraction data fortwo types of powder (powder a and powder b) having the same chemicalcomposition. Powder a has an apparent density of about 4.36 grams percube centimeter and powder b has an apparent density of about 5.08 gramsper cubic centimeter. While both powders a and b are very similar insize and morphology (powder b being marginally finer), a more uniformand resistant coating is obtained with powder a.

Referring to FIGS. 6 a and 6 b, these figures show two strips 400 offirst material 55 on which a coating of second material 60 (tungstencarbide) has been deposited. FIGS. 6 c and 6 d show the blade 100corresponding to the blades of FIGS. 6 a and 6 b, respectively, aftergrinding. In FIG. 6 a, the size of the powder particles constituting thesecond material is less than about 1 micrometer. In FIG. 6 b, the sizeof the powder particles constituting the second material is about 40micrometers. As can be seen in FIG. 6 b, because of the large particlesize, the coating of second material 60 protrudes from the top andbottom portions 35, 40 of the blade 100. By contrast, in the coating ofFIG. 6 a, the deposit of second material 60 remains confined at the tipof the blade. The configuration of FIG. 6 a is beneficial for grinding.

FIG. 7 shows a top view of the dispenser 520 in accordance with anembodiment of the invention. The dispenser 520 has a generally conicalannular shape, although it is contemplated that other shapes (e.g.square, rectangular, oval, polygonal) could be used to dispense themixture 542. The dispenser 520 includes a series of conical annularcavities designed to deliver the powder 542, inert shield gas 561 andlaser beam to a single focus point F. In an embodiment of thisinvention, the shielding gas 561 is Argon. As shown in FIG. 7, thedispenser 520 includes an outer cone 570 and a gas inlet 571 throughwhich the inert shield gas 561 is supplied. The dispenser 570 furtherincludes an inner cone 573 and inlets 574 a-b through which the mixture542 is supplied. A central cone 575 defines a passage in the dispenser520 to allow the projected radiation beam 555 to pass therethrough. Theinner cone 573 is arranged between the central cone 575 and the outercone 570 and defines a channel 576. The inner cone 573 and the outercone 570 define a channel 577 therebetween to allow the inert shield gas561 to flow therethrough. It will be appreciated that other arrangementsare contemplated. It will also be appreciated that additional or fewerchannels may be used to supply the mixture 542 to the strip 400.

The diameter of the periphery 562 of the central cone 575 is selectedalong with the distance D1 separating the dispenser 520 from the steelstrip 400 and the length of the channel 576 such that the particles ofthe mixture 542 fall under the action of gravity onto a predeterminedportion of the strip 400. Such predetermined portion generallycorresponds to the point of focus F of the beam of radiation 555 ontothe strip 400. The diameter of the inner periphery 562 is also selectedin order to allow the radiation beam 555 to pass through the dispenser520.

The inner shield gas 561 is configured to form a shield 546 around themixture 542 at a location near the point of focus F, as shown in FIG. 5.The shield 546 provides a protective atmosphere during deposition of themixture 542 of hard material (e.g. tungsten carbide) in order to preventoxidation of the strip 400. During use of the deposition station 500,the inner shield gas 561 is flushed from the inlet 571 down the channel577 to the strip in a manner that is such that the environment aroundthe melted portion of the strip 400 is non-oxidizing.

The dispenser 520 is fixedly mounted to a frame (not shown) ofdeposition station 500 and may be either stationary or movable in atleast three directions, e.g. x, y and z directions. A benefit of havinga movable dispenser 520 is that the position of the dispenser 520relative to the steel strip 500 can be accurately controlled. Variousmotors and actuators, such as electric, electromagnetic and/orpiezoelectric actuators, could be used to displace the dispenser 520.

Supply of the mixture 542 to the dispenser 520 is effected via theplurality of inlets 574 a-b. In one implementation, a container (notshown) is used to store the particles of mixture 542. The container isarranged to communicate with the plurality of inlets 574 a-b via one ormore conduits such that the mixture is conveyed to the predeterminedportion of the strip 400 via the channel 576 under the action ofgravity. In one embodiment of the invention, it is envisioned that thesupply of the mixture 542 be mechanically assisted with, for example, acompressed gas or a mechanical pusher.

The dispenser 520 may also include one or more shutters (not shown) toprevent particles of mixture 542 from exiting the nozzles 560 aftercompleting the deposition process. The shutters may be arranged on theinner periphery of the dispenser 520, or within the channels or on theupper portion of the dispenser.

Referring back to FIG. 5, the strip 400 may be moved in at least threedirections, x, y and z, relative to the beam of radiation 555 with theaid of an actuator 535. As shown in FIG. 5, the movable strip 400 ismoved under the radiation beam 555 along the x direction with the use oftwo rollers 544 a-b. The two rollers 544 a-b can be positioned with theactuator 535. One or more separate motors may be used to move the steelstrip 200 in the at least three directions, x, y and z. Examples ofactuators that may be used in an embodiment of the invention includeelectric and electromagnetic actuators. The position of the strip 400may be controlled with the aid of dedicated electronics and servocontrol systems. To that effect, a measurement system (not shown) may beused to measure the position of the moving strip 400 under the radiationbeam 555.

It will be appreciated that deposition of the mixture 542 of hardmaterial (e.g. tungsten carbide) and binder element could he carried outin an unprotective environment. In this implementation, oxidation of thestrip 400 will occur at the locations on the blade where the mixture 542is deposited. The oxidation could then be mechanically or chemicallyremoved after completing the deposition process. For example, it iscontemplated that an in-line polishing process using a wire brushing beapplied after deposition of the mixture 542 onto the strip 400.

An in-line measurement system 550 may be used to control thecharacteristics of the deposited mixture 542 onto the blade 100.Preferably, the measurement system 550 is a non-destructive opticalsystem, such as an ellipsometer, that controls the quality/compositionand thickness of the film mixture 542. The in-line measurement system550 may include an emitter 551 a and a detector 551 b. The emitter 551 ais configured to illuminate the portions of the strip 400 with aradiation beam. The radiation beam is reflected by the strip 400 andthen detected by the detector 551 b. The reflected radiation beam issubsequently analyzed with dedicated instrumentations in order tomeasure the characteristics of the coating of mixture 542. Preferably,the measurements are performed by the in-line measurement system 550after completing the deposition process. If the measured characteristicsof the strip 400 are not within specification, the portion of the steelstrip can be marked with a marker to indicate that the final bladeshould be rejected.

As shown in FIG. 5, a controller 545 is used to control the depositionprocess. The controller 545 may be operatively connected to thedispenser 520, the radiation source 505 and the actuator 535. Thecontroller 545 may be accessed by an operator to input the illuminationsettings, control the amount and flow of particles of the mixture 542 inthe dispenser 520 and/or the desired positioning of the strip 400 duringthe deposition process. In the configuration where multiple depositionheads or nozzles are used, the operator can input to the controller 545the desired composition in each deposition head. It will be appreciatedthat the positioning of the thin edge 17 of the strip 400 under theradiation beam 555, the amount of particles of mixture 542 and theillumination settings of the radiation source 505 may substantiallychange depending on the geometry and nature of the strip 400.

The binder element is selected to bind the hard material (e.g. tungstencarbide) to the melted material of the weld pool. All bonding betweenthe particles of the mixture 542 and the strip 400 is achieved bysolidification of the hard material (e.g. tungsten carbide)/binderelement within the weld pool. This results in a void free deposit ofhard material (e.g. tungsten carbide)/binder onto the strip 400. Anexample of binder that may be used in an embodiment of the inventionincludes cobalt. However, this is not limiting. It is contemplated thatadditional binders could be used in other embodiments of the invention.

The thickness of the deposit is controlled by the particle feed rate,the particle size, the illumination settings of the radiation source(e.g. energy, power, frequency of the radiation pulses) and the rate ofpassage of the strip 400 beneath the focused beam of radiation 555.These parameters are inputted and controlled by the controller 545. Thethickness of the deposit is measured by the measurement device 551.

In operation, the thin edge 17 of the strip 400 is continuously movedunder the radiation beam 555. It is desirable to carefully control thespeed of displacement of the strip 400 such that the thickness of thedeposit remains within specification at all times and to prevent theformation of voids in the deposit of the second material 60. The speedof the strip 400 may vary depending on the characteristics of the beamof radiation (e.g. wavelength and frequency, energy and power of thepulses), the size of the focus spot and the materials constituting thestrip 400. In an embodiment, the size of the voids present in thecoating of the second material is less than about 1% of the volume ofthe coating.

For example, if the speed of the strip 400 is not controlled, thedeposit of second material 60 may become undesirably porous. In oneembodiment, the limiting throughput speed at which a minimum of 0.15 mm,such as about 0.3 mm, deposition thickness of second material can beachieved is about 200 mm/minute to 300 mm/minute, such as 250 mm/minute.FIG. 8 a shows a cross section of the blade 100 obtained for a 250mm/minute deposit of second material. Because of the very low heatpenetration depth encountered with this technique there is littlebuild-up of heat in the strip 400. As a result, the strip isself-quenching, and heat transfer into the body is sufficiently rapid toexceed the critical cooling rate for full hardening. A narrow band ofuntempered martensite, which corresponds to the intermediate portion 65shown in FIG. 2 a, forms immediately behind the deposited layer.

Increasing the line speed significantly beyond 250 mm/minute (e.g.beyond 700 mm/minute), while still depositing a minimum of 0.3 mmdeposit thickness may create significant voids, as shown in FIG. 8 b. InFIG. 8 b, the speed of the strip is 1000 mm/minute. It has been foundthat, at higher processing speeds, the natural rate of cooling is highenough to result in cracking of the deposited layer, as shown in FIG. 8c. In one embodiment, the speed of the strip is less than 750 mm/minute.In another embodiment of the invention, the speed of the strip is lessthan 500 mm/minute.

Referring back to FIG. 3, after exiting the deposition station 500, thestrip 400 is delivered to a grinding machine. In an embodiment, at step391, the strip is recoiled and is transferred to a grinding machine forgrinding an edge of the strip and forming the first facets 45 a,b.

After grinding, at step 391, the edge of the strip 400 may be honed. Theprocess of honing creates the second facets 50 a,b and puts a secondangle α′ on top of the ground edge. This deeper honed angle gives astronger edge than the more shallow ground angle and allows to extendthe life span of the cutting edge. As a result the strip has an edgewith a double angle. In another embodiment, only a single angle may beprovided.

Finally, the processed steel strip is snapped along the length of thesteel strip at each score line to break the steel strip along the scorelines to produce a plurality of blades, at step 392.

A utility knife blade has been described in the foregoing embodiments.However, this is not limiting. It will be appreciated that other typesof blades can be manufactured in a similar manner as a utility knifeblade. Examples of blades that can be manufactured in accordance withthe process described above include TK blades, razor blades, carpetblades, scrapper blades, saw blades, hacksaw blades, and recip blades.

While the principles of the invention have been made clear in theillustrative embodiments set forth above, it will be apparent to thoseskilled in the art that various modifications may be made to thestructure, arrangement, proportion, elements, materials, and componentsused in the practice of the invention.

It will thus be seen that the objects of this invention have been fullyand effectively accomplished. It will be realized, however, that theforegoing preferred specific embodiments have been shown and describedfor the purpose of illustrating the functional and structural principlesof this invention and are subject to change without departure from suchprinciples. Therefore, this invention includes all modificationsencompassed within the spirit and scope of the following claims.

What is claimed is:
 1. A utility knife blade comprising: a portion madeof a first material; and an elongated portion made of a second material,the second material being harder than the first material and coated onthe first material by melting a powder of the second material on thefirst material, the elongated portion forming the tip of the blade,wherein the second material includes tungsten carbide particles embeddedin a soft binder, and wherein the size of at least 90% of the tungstencarbide particles is lower than about 5 micrometers.
 2. The utilityknife blade of claim 1, wherein the second material includes carbon in arange from about 3 to 7%.
 3. The utility knife blade of claim 2, whereincarbon is in a range from about 5 to 5.5%.
 4. The utility knife blade ofclaim 1, wherein the powder is made of particles having a size in arange from about 15 to 45 micrometers.
 5. The utility knife blade ofclaim 4, wherein the powder is made of particles having a size in arange from about 25 to 35 micrometers.
 6. The utility knife blade ofclaim 1, wherein the size of at least 95% of the tungsten carbideparticles is lower than about 2 micrometers.
 7. The utility knife bladeof claim 6, wherein the size of at least 99% of the tungsten carbideparticles is lower than about 2 micrometers.
 8. The utility knife bladeof claim 1, wherein the soft binder includes cobalt and chromium.
 9. Theutility knife blade of claim 8, wherein the second material includescobalt in a range from about 8 and 12% and chromium in a range fromabout 2 to 5%.
 10. The utility knife blade of claim 7, wherein cobalt isin a range from about 9.5 to 10.5% and chromium is in a range from about3.5 to 4.5%.
 11. The utility knife blade of claim 1, wherein the powderhas a density in a range from about 2 and 6 grams per cubic centimeter.12. The utility knife blade of claim 1, wherein the powder has a densityin a range from about 3 and 5 grams per cubic centimeter.
 13. Theutility knife blade of claim 1, wherein the powder is made ofsubstantially hollow particles having a size in a range from about 15 to45 micrometers.
 14. The utility knife blade of claim 1, wherein the sizeof the tungsten carbide particles after coating the second material onthe first material is substantially the same as the size of the tungstencarbide particles in the powder.
 15. The utility knife blade of claim 1,wherein the second material is coated on the first material by laserdeposition.
 16. The utility knife blade of claim 1, wherein the hardnessof the second material is greater than about 1,100 Hv.
 17. The utilityknife blade of claim 1, wherein the hardness of the first material is ina range from about 500 Hv to about 700 Hv.
 18. The utility knife bladeof claim 17, wherein the hardness of the first material is in a rangefrom about 630 Hv to about 650 Hv.
 19. The utility knife blade of claim1, wherein a thickness of the second material along a cross section ofsaid blade is in a range from about 0.1 mm to about 0.3 mm.
 20. Theutility knife blade of claim 1, wherein the first material is steel. 21.The utility knife blade of claim 1, wherein voids in the second materialrepresent less than about 1% of a total volume of the second material.22. A manufactured blade for a cutting tool comprising: a firstelongated portion made of a first material; and a second elongatedportion made of the first material and a second material, the secondmaterial being harder than the first material and deposited on the firstmaterial, the second elongated portion foaming the tip of the blade,wherein the first elongated portion defines a first cutting edge havinga first angle and the second elongated portion defines a second cuttingedge having a second angle, the first angle being smaller than thesecond angle, and wherein a transition from the first angle to thesecond angle occurs in a region of the blade made of the first materialthat has been re-hardened during deposition of the second material onthe first material.
 23. The blade of claim 22, wherein said region has ahardness lower than a hardness of the second material but greater than ahardness of the first material.
 24. The blade of claim 23, wherein thehardness of the second material is greater than about 1,100 Hv.
 25. Theblade of claim 23, wherein the hardness of the first material is in arange from about 500 Hv to about 700 Hv.
 26. The blade of claim 25,wherein the hardness of the first material is in a range from about 630Hv to about 650 Hv.
 27. The blade of claim 22, wherein a thickness ofthe second material along a cross section of said blade is in a rangefrom about 0.1 mm to about 0.3 mm.
 28. The blade of claim 22, wherein athickness of said region along a cross section of said blade is in arange from about 0.3 mm to about 0.4 mm.
 29. The blade of claim 22,wherein the second material occupies a volume greater than 50% of atotal volume of the second elongated portion.
 30. The blade of claim 22,wherein the second material occupies a volume greater than 70% of atotal volume of the second elongated portion.
 31. The blade of claim 22,wherein the second material is tungsten carbide.
 32. The blade of claim31, wherein a size of tungsten carbide particles is less than about 2micrometers.
 33. The blade of claim 31, wherein the second materialincludes a mixture of cobalt, chromium, carbon and tungsten.
 34. Theblade of claim 33, wherein cobalt is in a range of from about 9.5 to10.5 by weight of the second material, chromium is in a range of a fromabout 3.5% to 4.5% by weight of the second material and carbon is in arange of a from about 5% to 5.5% by weight of the second material. 35.The blade of claim 22, wherein the first material is steel.
 36. Theblade of claim 22, wherein voids in the second material represent lessthan about 1% of a total volume of the second material.
 37. Amanufactured blade for a cutting tool comprising: a portion made of afirst material; and an elongated portion made of the first material anda second material, the second material being harder than the firstmaterial and deposited on the first material, the elongated portionforming the tip of the blade, wherein the elongated portion forms afacet of the blade that is oriented at a non-zero angle relative to asurface of the portion of the blade, and wherein a transition from thesurface of the portion to the facet of the elongated portion occurs in aregion of the blade made of the first material that has been re-hardenedduring deposition of the second material on the first material.
 38. Theblade of claim 37, wherein said region has a hardness lower than ahardness of the second material but greater than a hardness of the firstmaterial.
 39. The blade of claim 38, wherein the hardness of the secondmaterial is greater than about 1,100 Hv.
 40. The blade of claim 38,wherein the hardness of the first material is in a range from about 500Hv to about 700 Hv.
 41. The blade of claim 40, wherein the hardness ofthe first material is in a range from about 630 Hv to about 650 Hv. 42.The blade of claim 40, wherein the second material is tungsten carbide.43. A manufactured blade for a cutting tool comprising: a portion madeof a first material and having a hardness in a range from about 500 Hvto about 700 Hv; and an elongated portion made of the first material anda second material, the second material being harder than the firstmaterial and deposited on the first material and having a hardnessgreater than about 1,100 Hv, the elongated portion forming the tip ofthe blade, wherein the elongated portion forms a facet of the blade thatis oriented at a non-zero angle relative to a surface of the portion ofthe blade, and wherein the second material includes tungsten carbideparticles that have a size less than about 5 micrometers.
 44. The bladeof claim 43, wherein the size of the tungsten carbide particles is lessthan about 2 micrometers.
 45. The blade of claim 43, wherein atransition from the surface of the portion to the facet of the elongatedportion occurs in a region of the blade made of the first material thathas been re-hardened during deposition of the second material on thefirst material.